In recent years, need of digital color proof (DDCP), particularly in the field of printing, has been increased accompanied with pervasion of an image forming technology from digital data.
In such DDCP, color reproducibility and stable reproducibility of printed matter are required and a laser thermal transfer technique has been adopted. Concretely, a technique, in which utilizing an ink sheet for laser thermal transfer, comprising a photo-thermal conversion layer and a colorant layer, and an image receiving sheet for laser thermal transfer, comprising an image receiving layer which receives an ink layer of the ink sheet and a layer capable of being softened by heat (thermally softening layer), and facing an ink layer surface of the above-described ink sheet to an image receiving layer surface of the above-described image receiving sheet, laser exposure from the ink sheet side is performed to thermally transfer an ink layer to an image receiving layer side by photo-thermal conversion and further to thermally transfer an image from an image receiving sheet carrying the image to a final image carrying element, has been disclosed.
Such a type of DDCP is able to output a final image on the same paper as printed matter, and is preferred because being applicable as a final proof sample in respect to providing a halftone output and utilizing printing pigments and printing paper for production. Further, various kinds of paper are utilized in printing, including such as art paper, coated paper, matte paper, slightly coated paper and uncoated paper.
Recently, there is increasing desire to utilize DDCP such as described above for a wider range of paper kinds. Corresponding to such desire, a technique, in which transfer property of from matte paper to wood free paper is improved by improving physical property of a thermally softening layer, is disclosed in Japanese Patent Publication Open to Public Inspection No. 2001-138648. However, a desired level of customers for a proof corresponding to printed paper for production means not only to being transferred on paper, but also how much similar is the paper to a printed mater with respect to both of image/non-image portions.
Many conventional techniques to control gloss relating to the following (1) to (3) are disclosed by such as an applicant of the present invention:
(1) A so-called ink-on recording method in which only an ink image is transferred to a final image carrying element after the ink image having been formed on an intermediate transfer medium,
(2) A method in which by enhancing thermal deform property of an intermediate transfer medium to increase the following ability to paper at the time of retransfer, a non-image portion of a proof being made to simulate the non-image portion of printing paper as it is,
(3) In a method of transferring an ink image together with a receiving layer, a method and a material, in which the surface of a receiving layer being roughened to simulate a non-image portion of a final image carrying element.
However, in an ink-on recording method of (1), there is a problem that gloss of an image portion is decreased due to an image portion being roughened at the time of retransfer and delamination, resulting in poor quality with respect to paper having high gloss such as art paper. In a method of (2), there are two problems to be solved. Firstly, to enhance thermal deform property without having a delaminatable intermediate layer which hardly causes thermal deformation, results in making a delaminating operation heavy and a final image carrying element being damaged in a quite high probability, because delamination surface follows the roughness of paper when an image is transferred to and delaminated from a final image carrying element. Secondly, with respect to paper having a smooth surface such as art paper, the surface gloss is not decreased as the surface of paper even with powerful heat and pressure, which is not preferable in respect to quality. In a method of (3), even with smooth art paper, gloss of a non-image portion can be adjusted to the same level as that of an aimed final image carrying element, more suitably than in a method of (2), without causing a damage in a image portion, since transfer is performed together with a roughened receiving layer. Therefore, the method is preferred in respect to adjusting gloss.
Further, various capability items other than gloss are required for such an intermediate transfer medium. For example, writing speed is an important item and increased sensitivity is also very frequently required. In view of these respects, an intermediate transfer medium having a roughened surface of such as a method of (3) described above can not be denied to be disadvantageous.
Further, as approach from a system in respect to writing speed, a method in which plural lasers are arranged in an alley to achieve high-speed writing is widely utilized in practical use. A solid image recorded by means of such a method may exhibit an uneven solid image quality, due to an effect of distribution of laser light intensity and an effect of a head period. In respect to such a phenomenon, a method of (3) was disadvantageous. That is, there was a problems to be solved that, because the moving distance of ink layer being transferred is large, unevenness depending on a laser alley unit is liable to occur due to a delicate difference in such as a cut of ink and a state of heating.